docs: def _check_invalid_longitudes(self):
          '''
          Checks to ensure that all longitudes are in the range -180. to 180
          '''
          idlon = self.strain.data['longitude'] > 180.
          if np.any(idlon):
              self.strain.data['longitude'][idlon] = \
                  self.strain.data['longitude'][idlon] - 360.